Electrolysis device

ABSTRACT

The present invention relates to an electrolysis device comprising an elementary assembly ( 10 ) made up of a membrane element ( 12 ) surrounded on either side by an electrode ( 11, 13 ), a rigid conducting plate ( 30 ), at least one electric conductor ( 21, 31 ) inserted between said elementary assembly ( 10 ) and said rigid conducting plate ( 30 ), said electric conductor ( 21, 31 ) being made up of a corrugated plate suitable for deforming and ensuring electric contact between said elementary assembly ( 10 ) and said rigid conducting plate ( 30 ). The device ( 100 ) also comprises a peripheral element ( 28, 38 ) at least partially surrounding said electric conductor ( 21, 31 ), said peripheral element ( 28, 38, 48, 58 ) being made of a material with a lower thermal expansion coefficient than the thermal expansion coefficient of the material of said electric conductor ( 21, 31 ).

The present invention relates to an electrolysis device such as the high temperature electrolysers that comprise an anion or proton exchange membrane.

The invention relates more particularly to the high temperature electrolysers that comprise a stack of elementary assemblies made up of a cathode, and electrolyte and an anode, separated by bipolar plates, also called interconnectors, which particularly ensure electrical continuity between the various elementary assemblies.

The invention may also relate to fuel cells to which the technological advances in high temperature electrolysers are directly applicable.

The current technologies of high temperature electrolysers, for example of the solid oxide electrolyser cell (SOEC) type or fuel cells are based on the use of two electrically conductive and porous electrodes separated by an electrolyte membrane that is electrically insulating and ionically (anions or protons) conductive, forming a structure called an elementary assembly.

In order to improve the efficiency of such an assembly, it is known to stack several elementary assemblies and connect them electrically in series, the different elementary assemblies being separated by means of a bipolar plate whose function is to conduct electricity.

Each bipolar plate has one surface that is in contact with the anode surface of the elementary assembly and one surface that is in contact with the cathode surface of the elementary assembly. The electrolysis device is made up of a stack of elementary assemblies, each elementary assembly being clamped between two bipolar plates, wherein the first bipolar plate must have good electrical contact with the cathode surface of the elementary assembly, and the second bipolar plate must have good electrical contact with the anode surface of the same elementary assembly.

Besides their function of ensuring electrical continuity between the various elementary assemblies inside an electrolysis device, the bipolar plate must perform additional functions such as ensuring a continuous supply of reagents and continuous extraction of products on the porous electrodes (anode and cathode).

It should also be noted that the bipolar plates may also include cooling elements to counteract any incidents of overheating in the stack.

The bipolar plates of the electrolysers and fuel cells have undergone significant development in the last few years, which has resulted in a number of different configurations.

In order to ensure that the electrolysis device functions in satisfactory conditions, and particularly that its internal resistance is a low as possible, the electrical contact between the bipolar plates and the elementary assemblies must be as good as possible.

However, given the geometrical tolerances involved in manufacturing bipolar plates, the depth dispersions of the channels for distributing the reagents and transporting the products away, defects in flatness, and more generally the geometrical defects of these plates, it is difficult to guarantee constant contact pressures between the bipolar plates and the elementary assemblies, and particularly to guarantee uniform pressures over the entire contact surface between the bipolar plates and the elementary assemblies.

In order to improve the electrical contacts between the bipolar plates and the assemblies, document FR2899386 suggests an elementary assembly if a fuel cell inserted between two bipolar plates, comprising an elastic electrically conducting element, particularly a corrugated metal strip, located between a bipolar plate and an elementary assembly in order to ensure electrical contact while at the same time compensate for the geometrical or dimensional irregularities of the bipolar plates and thereby to assure that the contact pressure is distributed evenly over the entire reactive surface of the elementary assembly.

However, this suggested type of electrolysis device is not able to assure optimum electrical contact in the face of the geometrical fluctuations brought about by the effects of thermal expansion.

Moreover, the corrugated metal strip disposed between each bipolar plate and an elementary assembly functions as a type of spring, exerting constant pressure and substantial stresses on the elementary assembly, even when it is cold, when the electrolysis device is not in operation, thus shortening its service life.

In this context, the object of the invention is to resolve the problems outlined in the preceding and to improve the electrical contact between the bipolar plate and the elementary assembly when such a device is operating at high temperature, and at the same time to reduce the stressed exerted on the elementary assembly when the device is not in operation.

To this end, the invention suggests an electrolysis device comprising:

-   -   an elementary assembly including a membrane element bordered on         either side by an electrode,     -   a rigid conductor plate, and     -   at least one electric conductor inserted between the elementary         assembly and the rigid conductor plate, the electric conductor         being made up of a corrugated plate that is able to undergo         deformation and ensure the electrical contact between the         elementary assembly and the rigid conductor plate;         the electrolysis device being characterized in that it comprises         a peripheral element that at least partially surrounds the         electric conductor, which peripheral element is made from a         material having a lower coefficient of thermal expansion than         that of the electric conductor material.

The term corrugated plate is understood to mean a plate made from sheet metal, one section of which is shaped in a periodic oscillating manner (that is to say an undulation), for example a sinusoidal, triangular, truncated triangular, or even a jagged slanted shape.

The periodic shape of the electric conductor thus enables an elastic function to be provided in the direction of the thickness of the device so as to ensure an electrical contact between the bipolar plates and the elementary assemblies despite the presence of geometrical or dimensional irregularities of the elements that make up the electrolysis device.

Thanks to the invention, it is possible to ensure electrical contact between the bipolar plates and the elementary assemblies at high temperature (that is to say above 500° C.) and to limit the deformations caused by thermal expansion of the electric conductor, particularly along an axis parallel to the direction of the undulation, significant thermal expansion along an axis parallel to the direction of undulation of the electric conductor that is capable of causing losses of electrical contact.

To this end, the peripheral element at least partly surrounding the electric conductor and having a coefficient of thermal expansion lower than the coefficient of thermal expansion of the electric conductor makes it possible to contain the deformations of the electric conductor due to thermal expansion in a plane parallel to the plane surface of the bipolar plates and the elementary assemblies.

Moreover, the particular positioning of the peripheral element around the electric conductor enables the deformation of the electric conductor due to thermal expansion to be directed according to its thickness in such manner that it compensates for any deformations of the device components due to thermal expansion and/or the flaws and other geometrical irregularities of the stack and to ensure an electrical contact between the bipolar plate and the elementary assembly.

The electrolysis device according to the invention may also include one or more of the features listed in the following, either individually or in any technically possible combination:

-   -   the peripheral element is made from a ceramic material;     -   the ceramic material is a ceramic having the same empirical         formula as the membrane element;     -   the peripheral element comprises a first opening and a second         opening located on either side of the electric conductor, said         openings allowing the circulation of a fluid through the         electric conductor;     -   the peripheral element is made up of two ring segments         positioned opposite one another;     -   the peripheral element is a complete circular ring comprising         two thinner sections positioned opposite one another;     -   the at least one electric conductor is permanently joined at         least in part to the peripheral element;     -   the peripheral element attaches at least ten waves of the at         least one electric conductor;     -   the peripheral element attaches at least the last two waves at         each end of the corrugation of the at least one electric         conductor;     -   the at least one electric conductor comprises a section that         defines a periodic oscillating motion of sinusoidal shape;     -   the at least one electric conductor comprises a section that         defines a periodic oscillating motion of triangular or truncated         triangular shape;     -   the electric conductor is made from a material containing nickel         alloy and/or stainless steel;     -   the electrolysis device comprises a series of stacks formed by:         -   a rigid conducting plate;         -   a first anodic electric conductor in contact with the             conducting plate at least partially surrounded by a first             peripheral element;         -   an elementary assembly made from a membrane element bordered             on either side by an anode and a cathode, the anode being in             contact with the anodic electric conductor;         -   a second, cathodic electric conductor in contact with the             cathode of the elementary assembly at least partially             surrounded by a second peripheral element.     -   the first peripheral element is furnished with a first opening         and a second opening, arranged on opposite sides of first anodic         electric conductor; the second peripheral element is furnished         with a first opening and a second opening arranged on opposite         sides of the first cathodic electric conductor; the first         peripheral element and the second peripheral element being         arranged such that the opening in the first peripheral element         are perpendicular to the openings in the second peripheral         element.

Other features and advantages of the invention will be more evident upon reading the description thereof provided in the following, which is provided for purely illustrative and non-limiting purposes, with reference to the accompanying drawing, in which:

FIG. 1 is a top view of the section of an electrolysis device according to the invention showing cross sectional lines for the purposes of the following figures;

FIG. 2 is a schematic representation of a first frontal cross section of the electrolysis device of FIG. 1, showing a stack of elementary assemblies;

FIG. 3 is a schematic representation of a second frontal cross section of the electrolysis device, showing a stack of elementary assemblies;

FIG. 4 is a more detailed view of a stack of two successive elementary assemblies of the device shown in FIG. 2;

FIG. 5 shows a first embodiment of an anodic electric conductor component of the electrolysis device according to the invention;

FIG. 6 shows a first embodiment of a cathodic electric conductor component of the electrolysis device according to the invention;

FIG. 7 shows a second embodiment of an anodic electric conductor component of the electrolysis device according to the invention;

FIG. 8 shows a second embodiment of a cathodic electric conductor component of the electrolysis device according to the invention;

FIG. 9 is a schematic half profile of the anodic electric conductor of FIG. 6;

FIG. 10 is a schematic half profile of the cathodic electric conductor of FIG. 7;

FIG. 11 is a schematic half profile of the electric conductor according to the embodiment of FIGS. 7 and 8.

In all the figures, common elements are identified with the same reference numbers unless indicated otherwise.

FIG. 1 is a top view of an electrolysis device 100 according to the invention, comprising a plurality of elementary assemblies stacked in a casing 1 that forms a closed containment tube. A bottom cover 6 and a top cover 5 close casing 1 hold the assembly together.

The various cross sectional lines along which the views of the following FIGS. 2, 3 and 4 are illustrated are shown in FIG. 1.

FIG. 2 shows a first frontal cross section along plane A-A of electrolysis device 100 according to the invention shown in FIG. 1.

FIG. 3 shows a second frontal cross section along plane B-B of electrolysis device 100 according to the invention shown in FIG. 1.

FIG. 4 is a view in greater detail of a stack of two successive elementary assemblies 10 of the device 100 shown in FIG. 2, according to first cross sectional plane A-A.

Electrolysis device 100 comprises a stack of a plurality of elementary assemblies 10 separated by bipolar plates 30. Nine elementary assemblies 10 have been illustrated in this stack, but the number of elementary assemblies is not fixed, such an electrolysis device may comprise any number of elementary assemblies.

Each elementary assembly 10 comprises at least one assembly referred to as the electrolytic cell and formed by a cathode 13, an electrolyte 12, and an anode 11, positioned in that order from top to bottom, electrolyte 12 being sandwiched between anode 11 and cathode 13.

Cathode 13 and anode 11 are electrically conductive porous electrodes whereas electrolyte 12 is a membrane that insulates electrically and conducts ions (anions or protons), typically made from a ceramic material.

According to a first advantageous embodiment of the invention, besides the electrolytic cell elementary assembly 10 includes two diffusion layers 18, 19 that enclose cathode 13 and anode 11 of the electrolytic cell and particularly promote diffusion of the reagents and extraction of the products in contact with the electrodes (anode and cathode). Diffusion layers 18, 19 are porous metal layers that also enhance the distribution of electrical potential on the cathode and/or the anode and to reinforce the electrolytic cell so that it is able to withstand any pressure differential through the electrolytic cell.

Bipolar plates (or interconnectors) 30 are interposed between these various elementary assemblies 10. A cathodic closing connector 15 closes the stack at the top, in the same way an anodic support connector 16 closes the stack at the bottom.

The stack is held in position by containment casing 1 that surrounds all of the assemblies 10 for the full length of the stack, and which includes an upper cover 5 and a lower cover 6 which delimit the extremities of containment casing 1. The entire assembly is held together by a plurality of rods 7 that pass through device 100 vertically, sixteen in the example shown in FIGS. 1, 2 and 3, and by a plurality of nuts 8 that are able to exert a clamping pressure on covers 5 and 6.

Electrolysis device 100 further comprises at least one reagent distribution channel 22 and at least one product extraction channel 23 passing vertically through electrolysis device 100. Channels 22 and 23 communicate respectively with inlet conduits 24 and outlet conduits 25, which are essentially horizontal and able to distribute the reagents or extract the products formed by the electrolysis reaction at each electrode 11, 13 of each elementary assembly 10 of the stack.

The device 100 shown in FIGS. 1, 2, 3 and 4 is a high temperature electrolyser comprising a proton exchange membrane. However, the architecture of the device and the stack shown may be equally well applied to an electrolyser that comprises an anion exchange membrane or a fuel cell type electrolysis device; the channels for distributing the reagents and extracting the products would then be adapted according to the reagents to be distributed and the products to be extracted at the cathode and the anode of each elementary assembly 10.

In the example of the electrolyser comprising a proton exchange membrane illustrated in FIGS. 1, 2, 3 and 4, the reagent is a water vapour gas (H₂O) supplied to anode 11 via feed channel 22 and the product is hydrogen (H₂) collected at cathode 13 and extracted via extraction channel 23. The electrolysis reaction also produces oxygen (O₂) at the anode, mixing with the water vapour (H₂O) that has not reacted and needs to be extracted. To this end, device 100 comprises with a second extraction channel 23′ for extracting the water vapour-oxygen mixture (H₂O+O₂) that cooperates with a second extraction conduit 25′ at anode 11 of elementary assembly 10. In order to create a flow of gas circulating on upon contact with cathode 13 for extracting the hydrogen product (H₂), hydrogen is introduced into device 100 via a second distribution channel 22′ and fed to cathode 13 through a second feed conduit 24′.

Channels 22, 22′, 23 and 23′ and conduits 24, 25, 24′ and 25′ are arranged such that the flow of incoming gas (H₂O) and the flow of outgoing gas (H₂ and O₂) are kept separate, and he flow of hydrogen (H₂) and the flow of oxygen (O₂) generated by the electrolysis reaction are kept separate, in order to prevent these two gases from mixing, which might cause the device to catch fire or explode. The separation of the different gases is particularly effected by bipolar plate 30, which is impermeable to gases.

According to a preferred embodiment of the invention, bipolar plate 30 is a plate several millimetres thick, typically from 4 to 6 mm thick for an SOEC type electrolyser, so that it is able to withstand the possible differences in flow pressures between the anodic portion and the cathodic portion of elementary assemblies 10. Bipolar plate 30 is electrically insulated from casing 1 by a brazing material or by insulating sealing means (not shown). According to a preferred embodiment of the invention, bipolar plate 30 is made from a nickel alloy, for example of the type Inconel 625, Inconel 718, Nimonic 80A or also Haynes 230.

In order to ensure a good electrical contact between elementary assembly 10 and bipolar plates 30, device 100 includes electrically conductive components 21 and 31, which assure an electrical contact between each bipolar plate 30 and each elementary assembly 10, electrical conductors 21, 31 having a certain elasticity in the direction of the thickness (along axis ZZ).

According to the first embodiment of the invention, electrolysis device 100 comprises a cathodic electrical conductor 21 in contact with the cathodic surface of elementary assembly 10 and the cathodic surface of bipolar plate 30, and comprises an anodic electrical conductor 31, thinner than cathodic electrical conductor 21, in contact with the anodic surface of elementary assembly 10 and the anodic surface of bipolar plate 30. According to the particular embodiment shown in FIGS. 2, 3, and 4, anodic electrical conductor 31 is thinner than cathodic electrical conductor 21; however, the electrical conductors 21 and 31 may have the same thickness or different thicknesses, the thicknesses of the electrical conductors being determined by the design of the electrolysis device.

According to the particular embodiment shown in FIGS. 2, 3, and 4, the upper surface of anodic electrical conductor 31 is in contact with porous anodic diffusion layer 19, and the lower surface thereof is in contact with the anodic face of bipolar plate 30.

According to the same embodiment, the lower surface of cathodic electrical conductor 21 is in contact with porous cathodic diffusion layer 18, and the upper surface thereof is in contact with the cathodic surface of bipolar plate 30.

First embodiment of an anodic electric conductor 31 and a cathodic electric conductor 21 are shown in greater detail in FIGS. 5 and 6 respectively.

Anodic electric conductor 31 is made up of a circular corrugated plate whose cross section along a plane XX-ZZ follows a sinusoidal pattern shown in FIG. 9, and a metal ring 39 at least partially surrounding the corrugated plate.

FIG. 5 shows anodic electric conductor 31 at least partially surrounded by a ceramic ring 38; ceramic ring 38 concentrically surrounds metal ring 39 of anodic electric conductor 31. Metal ring 39 is a fastening means between anodic conductor 31 and ceramic ring 38, metal ring 39 being brazed onto ceramic ring 38. Other means for fastening ceramic ring 38, of the mortise and tenon type system or even by pressing means are conceivable.

The circular shape of anodic electric conductor 31 is necessitated by the overall shape of the electrolysis device, the electrolysis device being a device with a circular cross section.

Anodic electric conductor 31 is a thin corrugated plate having a thickness in the order of a few tenths of a millimetre, typically 0.2 mm, and of which the corrugation amplitude is between 4 and 20 mm. The term undulation refers to an oscillating shape formed alternatingly by a high wave VH and a low wave VB, along an axis parallel to axis XX shown in FIG. 5. The corrugation amplitude is understood to be the distance between the projections at the tips of high wave VH and at the tips of low wave along axis ZZ.

The first embodiment of anodic electric conductor 31 shown in FIG. 5 shows a succession of ten undulations or an alternating series of ten high waves VH and ten low waves VB. FIG. 9 is a schematic representation of a cross section of anodic electric conductor 31 and of the position of the various waves, wave V1 being the central low wave of anodic electric conductor 31 and wave V10 representing the terminal wave of the conductor.

It will be noted that contact between the anodic surface of bipolar plate 30 and the anodic diffusion layer 19 is provided by the tips of each high wave VH and each low wave VB of each undulation.

The sinusoidal shape of anodic electric conductor 31 enables an elasticity to be obtained in the direction of the thickness, that is to say along vertical axis ZZ, which is essential for establishing and maintaining the electric contact between bipolar plate 30 and elementary assembly 10 when the various stacks are fitted.

In fact, when electrolysis device 100 is being assembled, anodic electric conductors 31 are slightly deformed along axis ZZ by compression in order to guarantee the electrical contact.

Ceramic ring 38 and metal ring 39 are located on the periphery of anodic electric conductor 31.

According to the first, non-limiting embodiment shown in FIG. 5, ceramic ring 38 is divided into two distinct circular segments, arranged diametrically opposite one another so as to create a lateral opening on either side of anodic electric conductor 31 that allows water vapour to flow in direction XX parallel to the undulation of anodic electric conductor 31 as well as the passage of the gas flow made up of a mixture of water vapour (H₂O) and oxygen (O₂) produced by the electrolysis reaction, the direction of circulation of the flows of water vapour (H₂O) and the mixture of water vapour/oxygen being represented by arrows in FIG. 5.

In general, anodic electric conductor 31 is made from a material having good electrical conductivity at high temperature (that is to say above 500° C.) and low resistance on contact with the anodic and cathodic elements of elementary assemblies 10. Anodic electric conductor 31 must also be highly corrosion-resistant, have good creep properties, a high yield strength at high temperature and good ductility and welding properties.

Accordingly, anodic electric conductor 31 and metal ring 39 are made from a nickel alloy of type Inconel 625, and ceramic ring 38 is made from a ceramic material identical to the ceramic material of electrolyte 12 having a coefficient of thermal expansion lower than that of anodic electric conductor 31.

Thus, by way of example, coefficient of thermal expansion α of the electric conductor made from Inconel 625 is 14.5×10⁻⁶K¹ whereas coefficient of thermal expansion α of the ceramic ring is 11.8×10⁻⁶K¹.

Since ceramic ring 38 around the outside of anodic electric conductor 31 is less susceptible to thermal expansion, it serves to restrict the thermal expansion of anodic electric conductor 31, mainly along axis YY, when the electrolysis device is in operation.

To a lesser degree, ceramic ring 38, which is attached permanently to at least part of anodic electric conductor 31, also limits the thermal expansion of anodic electric conductor 31 along axis XX.

Besides limiting the thermal expansion of anodic electric conductor 31 along axes XX and YY, ceramic ring 38 also serves to amplify the vertical deformation of anodic electric conductor 31 along axis ZZ, thus ensuring permanent electrical contact between elementary assembly 10 and bipolar plate 30 at high temperatures (that is to say above 500° C.).

Thus deformation in the thickness, along axis ZZ, serves to guarantee electrical contact between the elementary assembly and the bipolar plate despite the presence of geometrical imperfections of such an assembly, caused by tolerances, flatness defects and the like.

In addition, electric conductor 31, which begins to deform along axis ZZ under the effect of thermal expansion as the temperature rises, serves to reduce the stresses of pressure when cold between the bipolar plate and the elementary assembly when the electrolysis device is not in operation.

FIG. 9 is a schematic representation of the cross section of a half profile of anodic electric conductor 31 on which various waves forming the corrugations are referenced. The wave referenced V1 corresponds to the centre wave of anodic electric conductor 31 and referenced wave V10 corresponds to the terminal wave; thus, anodic electric conductor 31 includes at least nine waves on either side of the centre wave referenced V1.

Ceramic ring 38 is advantageously circular in shape and is joined to anodic electric conductor 31 via at least five successive waves on each side of centre wave V1.

Similarly to the preceding description cathodic electric conductor 21, shown in FIG. 6, comprises a corrugated circular plate, of which the cross section along plane XX-ZZ has a sinusoidal function shown in FIG. 10, and a metal ring 29 that at least partially surrounds the corrugated plate.

FIG. 6 shows anodic electric conductor 21 at least partially surrounded by a ceramic ring 28; ceramic ring 28 encircles metal ring 29 of anodic electric conductor 21 concentrically. Metal ring 29 is a means for fastening anodic conductor 21 to ceramic ring 28, metal ring 29 being brazed onto ceramic ring 28. Other means for fastening ceramic ring 38, of the mortise and tenon system type, or using pressing methods are also conceivable.

The circular shape of cathodic electric conductor 21 is necessitated by the overall shape of the electrolysis device, the electrolysis device being a device with a circular cross section

Cathodic electric conductor 21 is a thin corrugated plate having a thickness in the order of a few tenths of a millimetre, typically 0.2 mm, and of which the corrugation amplitude of cathodic electric conductor 21 is between 4 and 20 mm.

The first embodiment of cathodic electric conductor 21 shown in FIG. 6 shows a succession of seven undulations or an alternating series of seven high waves VH and seven low waves VB. FIG. 10 is a schematic representation of a cross section of cathodic electric conductor 21 and of the position of the various waves, wave V1 being the central high wave of cathodic electric conductor 21.

It will be noted that contact between the cathodic surface of bipolar plate 30 and the cathodic diffusion layer 18 is provided by the tips of each high wave VH and each low wave VB of each undulation.

The sinusoidal shape of cathodic electric conductor 21 enables an elasticity to be obtained in the direction of the thickness, that is to say along vertical axis ZZ, which is essential for establishing and maintaining electric contact between bipolar plate 30 and elementary assembly 20 when the various stacks are fitted.

In fact, when electrolysis device 100 is being assembled, cathodic electric conductors 21 are slightly bowed along axis ZZ by compression in order to guarantee electrical contact.

According to the first, non-limiting, embodiment shown in FIG. 6, ceramic ring 28 is divided into two distinct circular segments, arranged diametrically opposite one another so as to create a lateral opening on either side of cathodic electric conductor 21 that allows hydrogen (H₂) to flow in direction YY perpendicular to the direction of undulation of cathodic electric conductor 21, the direction of circulation of the flow of hydrogen gas (H₂) being represented by an arrow in FIG. 6.

Thus, cathodic electric conductor 21 and anodic electric conductor 31 are arranged such that their openings are positioned perpendicularly to each other so as to facilitate the flows of gases into and out of device 100. However, depending on the design of the electrolysis device it is possible to located electric conductors 21 and 31 such that their respective openings are located at an angle other than 90° with respect to each other.

Cathodic electric conductor 21 is generally made from the same materials as anodic electric conductor 31 described in the preceding. It should be noted that cathodic electric conductor 21 must also be resistant to embrittlement by hydrogen (H₂).

Ceramic ring 28 around the outside of cathodic electric conductor 21 and also undergoes less thermal expansion than the conductor, thus limiting the thermal expansion of cathodic electric conductor 21, particularly along axis XX, when electrolysis device 100 is in operation.

To a lesser degree, ceramic ring 28, which is attached permanently to at least part of cathodic electric conductor 21, also limits the thermal expansion of cathodic electric conductor 21 along axis YY.

Besides limiting the thermal expansion of cathodic electric conductor 21 along axes XX and YY, ceramic ring 28 also serves to amplify the vertical deformation of cathodic electric conductor 21 along axis ZZ, thus ensuring permanent electrical contact between elementary assembly 10 and bipolar plate 30 at high temperatures (that is to say above 500° C.).

In addition, the electric conductor, which begins to deform along axis ZZ under the effect of thermal expansion as the temperature rises, serves to reduce the stresses of pressure when cold between the bipolar plate and the elementary assembly when the electrolysis device is not in operation.

FIG. 10 is a schematic representation of the cross section of a half profile of cathodic electric conductor 21 on which the various waves forming the corrugations are referenced. The wave referenced V1 corresponds to the centre high wave of cathodic electric conductor 21 and referenced wave V7 corresponds to the terminal wave; thus, cathodic electric conductor 21 includes at least six waves on either side of the centre wave referenced V1.

Ceramic ring 28 is advantageously circular in shape and is joined to cathodic electric conductor 21 via at least the two terminal waves from V5 to V7 of cathodic electric conductor 21.

FIGS. 7 and 8 illustrate a second embodiment of an anodic electric conductor 51 and a second embodiment of a cathodic electric conductor 41.

The anodic conductor 51 and the cathodic conductor 41 shown in FIGS. 7 and 8 follow the same characteristic principles as anodic conductor 31 and cathodic conductor 21 described previously with reference to FIGS. 5 and 6. In the following, only the differing elements specific to this second embodiment will be described in detail.

In this second embodiment, electric conductors 51, 41 do not have a section with a sinusoidal shape, but instead a section that is essentially accordion shaped, or triangular, the extremities of which are truncated to form flat zones that are capable of assuring electrical contact between the bipolar plate and the elementary assembly. The cross section along line XX-ZZ of electric conductors 51, 41 is represented schematically in the illustration of FIG. 11.

In this second embodiment, ceramic rings 58 and 48 are complete circular rings located around the outside of electric conductors 51, 41.

Circular ceramic rings 58, 48 comprise two thinner sections 58 b, 48 b such that they create a lateral opening on either side of electric conductors 51, 41 for the passage of a gas stream.

Thinner sections 58 b are arranged so as to allow the passage of the water vapour gas stream (H₂O) and the flow of water vapour mixed with oxygen (H₂O+O₂) gas stream in direction XX parallel to the corrugation of anodic electric conductor 51.

Thinner sections 48 b are arranged so as to allow the passage of the hydrogen (H₂) gas stream in direction YY perpendicularly to the corrugation of cathodic electric conductor 41.

This second embodiment of the ceramic rings 58, 48 thus helps to improve the installation of the electric conductor in the electrolysis device and to guarantee that it will be held securely in place within the stack.

Moreover, this embodiment makes it possible to simplify the process of manufacturing electric conductors.

The electric conductors according to the invention are typically produced by bending, forming or pressing.

The ceramic rings according to the invention enable the flexible electric conductors to be constricted when the device is in operation by using materials having different coefficients of thermal expansion. The position of the ceramic rings and their dimensions thus enable the vertical deformation along axis ZZ to be amplified under the effects of the thermal expansion of the electric conductor, while at the same time limiting thermal expansion along axes XX and YY.

The electric conductors are located in the passage of the incoming and outgoing gas streams, their particular shapes thus enable them not to obstruct the circulation of the gases in the conduits while minimising pressure loss.

By virtue of its shape and dimensions, the anodic electric conductor forces the stream of water vapour to enter the anodic diffusion layer or the anode. In the same way, the shape and dimensions of the cathodic electric conductor allows the hydrogen gas stream to pass and minimises losses of pressure.

The device according to the invention also serves to ensure that contact pressures are distributed evenly over the entire reactive surface of the elementary assembly while at the same time reducing the contact pressures on the elementary assembly at cold, and particularly on the electrolytic membrane.

Moreover, it should be noted that as the contact pressure is increased, so the electrical resistance of the device becomes weaker. Thus, the device according to the invention helps not only to prevent the stacks from being overstressed at cold, thereby making it easier to install such a device, but also to absorb the geometrical irregularities of the stacks at high temperatures while reducing electrical losses. The invention has been described in principle for a high temperature electrolyser comprising a Protonic Ceramic Electrolyser Cell (PCEC) type proton conducting membrane; however, the invention is equally applicable both for PCEC and Solid Oxide Electrolyser Cell (SOEC) electrolysers. In fact, both electrolyser types are electrolysers that operate at high temperature and in which problems associated with differences in thermal expansion between the membrane and the electrodes can occur.

The invention has been described in principle for a high temperature electolyser comprising a proton conducting membrane; however, the invention is equally applicable to fuel cells, typically of the SOFC type, to which the technological advances in high temperature electrolysers may be applied directly. 

1. An electrolysis device comprising: an elementary assembly made from a membrane element bordered on either side by an electrode, a rigid conductor plate, at least one electric conductor inserted between the elementary assembly and the rigid conductor plate, the electric conductor being made up of a corrugated plate that is able to undergo deformation and ensure the electrical contact between the elementary assembly and the rigid conductor plate; the electrolysis device being characterized in that it comprises a peripheral element that at least partially surrounds the electric conductor, which peripheral element is made from a material having a lower coefficient of thermal expansion than the coefficient of expansion of said electric conductor material.
 2. The electrolysis device as recited in claim 1, wherein the peripheral element is made from a ceramic material.
 3. The electrolysis device as recited in claim 2, wherein the ceramic material is a ceramic having the same empirical formula as the membrane element.
 4. The electrolysis device as recited in claim 1, wherein the peripheral element comprises a first opening and a second opening located on either side of the electric conductor, said openings allowing the circulation of a fluid through the electric conductor.
 5. The electrolysis device as recited in claim 1, wherein the peripheral element is made up of two ring segments positioned opposite one another.
 6. The electrolysis device as recited in claim 1, wherein the peripheral element is a complete circular ring comprising two thinner sections positioned opposite one another.
 7. The electrolysis device as recited in claim 1, wherein the at least one electric conductor is permanently joined at least in part to the peripheral element.
 8. The electrolysis device as recited in claim 1, wherein the peripheral element attaches at least ten waves of the at least one electric conductor.
 9. The electrolysis device as recited in claim 1, wherein the peripheral element attaches at least the last two waves at each end of the corrugation of the at least one electric conductor.
 10. The electrolysis device as recited in claim 1, wherein the at least one electric conductor comprises a section that defines a periodic oscillating motion of sinusoidal shape.
 11. The electrolysis device as recited in claim 1, wherein the at least one electric conductor comprises a section that defines a periodic oscillating motion of triangular or truncated triangular shape.
 12. The electrolysis device as recited in claim 1, wherein the electric conductor is made from a material containing nickel alloy and/or stainless steel.
 13. The electrolysis device as recited in claim 1, further comprising a series of stacks formed by: a rigid conducting plate; a first anodic electric conductor in contact with the conducting plate at least partially surrounded by a first peripheral element; an elementary assembly made from a membrane element bordered on either side by an anode and a cathode, the anode being in contact with the anodic electric conductor; a second, cathodic electric conductor in contact with the cathode of the elementary assembly at least partially surrounded by a second peripheral element.
 14. The electrolysis device as recited in claim 13, wherein: the first peripheral element is furnished with a first opening and a second opening, arranged on opposite sides of the first anodic electric conductor; the second peripheral element is furnished with a first opening and a second opening arranged on opposite sides of the second cathodic electric conductor; the first peripheral element and the second peripheral element being arranged such that the openings in the first peripheral element are perpendicular to the openings in the second peripheral element. 